Product Info

Plastic injection moulding defects such as warping, short shot, and flash often lead to higher costs and wasted production time. This article explains how to analyse and solve these problems systematically, with insights from Muto (Thailand), a one-stop provider for injection moulding services.


■ Injection Molding is More Than Just “Injecting Plastic”
While plastic injection moulding (Plastic Injection Moulding) may appear straightforward, the real complexity lies in the details. Small errors in mould design, injection parameters, cooling system, or material selection can create major defects.

The most common issues include:

- Warping: Part deformation after cooling
- Short Shot: Incomplete filling of the mould
- Flash: Excess plastic along parting lines

Based on Muto (Thailand)’s experience, here are the most frequent problems, their causes, and effective countermeasures.


1. Warping – Deformation After Cooling
Symptoms: Parts become bent, twisted, or dimensionally unstable.

> Root Causes:
- Inconsistent wall thickness
- Uneven mould temperature
- Poor cooling distribution
- Variations in material shrinkage

> Analysis Methods:
- 3D measurement comparison
- Mould flow simulation
- Coolant flow rate inspection

> Solutions:
- Redesign mould for balanced cooling
- Select materials with lower shrinkage
- Use zone-based mould temperature control
- Adjust packing pressure and cooling time


2. Short Shot – Incomplete Filling
Symptoms: Parts are not completely filled, leaving voids or missing sections.

> Root Causes:
- Insufficient injection pressure
- High flow resistance in runners or gates
- The material is cooling too quickly
- Poor venting is causing air traps

> Analysis Methods:
- Inspect repeated short shot locations
- Use CAE software for flow simulation
- Check flow balance in the runner system

> Solutions:
- Increase injection speed and pressure
- Resize gate and runner dimensions
- Improve mould venting design
- Optimise barrel and mould temperature


3. Flash – Excess Plastic Along Parting Lines
Symptoms: Thin, unwanted plastic forms along mould parting lines.

> Root Causes:
- Mould wear or poor alignment
- Insufficient clamping force
- Over-pressurisation during injection
- Contaminants between mould surfaces

> Analysis Methods:
- Inspect mould parting line
- Check mould flatness and surface conditions
- Monitor injection pressure at flash-prone areas

> Solutions:
- Repair and maintain mould regularly
- Adjust clamping force to match injection load
- Lower injection pressure and holding time
- Clean mould surfaces before each run


4. Preventing Defects Through Precision and Control
Rather than fixing problems after they occur, Muto (Thailand) emphasises prevention at the design stage:

- Mould design with flow simulation analysis
- Accurate parameter setting by material type
- High-precision injection moulding machines
- Quality inspection at every stage of production


■ Why Choose Muto (Thailand) for Injection Moulding?
Muto (Thailand) provides end-to-end plastic injection solutions, covering mould design, fabrication, injection, finishing, assembly, and inspection.

Our key strengths include:

- Advanced simulation and measurement technologies
- Engineering expertise in both moulds and materials
- In-house quality control to reduce defects
- Flexible support for both prototype and mass production

👉 If your factory is facing defects or inconsistencies in plastic injection moulding, Muto (Thailand) can help analyse, solve, and optimise your process for better quality and efficiency.

For more information, please [contact Muto (Thailand)](INSERT_LINK_HERE) or download our detailed service PDF.


#PlasticInjectionMolding #InjectionMolding #PlasticParts #MoldDesign #ManufacturingSolutions #OEM #MutoThailand #IndustrialParts